A Model for Manganese interaction with Deinococcus radiodurans proteome network involved in ROS response and defense.

A complex network of regulatory proteins takes part in the mechanism underlying the radioresistance of Deinoccocus radiodurans bacterium (DR). The interaction of Mn(II) ions with DR-proteins and peptides seems to be responsible for proteins protection from oxidative damage induced by Reactive Oxygen Species during irradiation. In the present work we describe a combined approach of bioinformatic strategies based on structural data and annotation to predict the Mn(II)-binding proteins encoded by the genome of DR and, in parallel, the same predictions for other bacteria were performed; the comparison revealed that, in most of the cases, the content of Mn(II)-binding proteins is significantly higher in radioresistant than in radiosensitive bacteria. Moreover, we report the in silico protein-protein interaction network of the putative Mn(II)-proteins, remodeled in order to enhance the knowledge about the impact of Mn-binding proteins in DR ability to protect also DNA from various damaging agents such as ionizing radiation, UV radiation and oxidative stress.

DNA content alterations in Tetrahymena pyriformis macronucleus after exposure to food preservatives sodium nitrate and sodium benzoate.

The toxicity, in terms of changes in the DNA content, of two food preservatives, sodium nitrate and sodium benzoate was studied on the protozoan Tetrahymena pyriformis using DNA image analysis technology. For this purpose, selected doses of both food additives were administered for 2 h to protozoa cultures and DNA image analysis of T. pyriformis nuclei was performed. The analysis was based on the measurement of the Mean Optical Density which represents the cellular DNA content. The results have shown that after exposure of the protozoan cultures to doses equivalent to ADI, a statistically significant increase in the macronuclear DNA content compared to the unexposed control samples was observed. The observed increase in the macronuclear DNA content is indicative of the stimulation of the mitotic process and the observed increase in MOD, accompanied by a stimulation of the protozoan proliferation activity is in consistence with this assumption. Since alterations at the DNA level such as DNA content and uncontrolled mitogenic stimulation have been linked with chemical carcinogenesis, the results of the present study add information on the toxicogenomic profile of the selected chemicals and may potentially lead to reconsideration of the excessive use of nitrates aiming to protect public health.